PhotoSocial media users compromise their privacy all the time. They post pictures while they are on vacation, for example, advertising the fact they aren't at home. They reveal other personal information that ought to be private.

But the social media infrastructure may also present some privacy problems. Chris Weidemann, a graduate student at the University of Southern California (USC), has focused his efforts on Twitter, finding that some Twitter users may be inadvertently revealing their location through updates on the social media channel.

“Really there are four ways a user can give away information,” Weidemann said in an interview. “The first, a user can geo-enable their tweets – meaning they include GPS coordinates. Roughly four to eight percent of all Tweets are geo-enabled - that's 30 million Tweets a day that have GPS coordinates associated with them. This provides accuracy down to the five to 50 foot level, depending on the mobile device the user is using and if they're indoors or outdoors.”

This vulnerability in compounded when a user with geo-enabled Tweets makes reference to a personally identifiable feature that provides additional metadata about the location. For example, someone might Tweet "I just got home from a long day and now I just want to watch TV." Weidemann says that could tell someone, should they want to know, where “home” is.

TMI

A third way users provide location data is when they simply broadcast too much information. For example, someone may Tweet they are meeting friends at a particular restaurant for dinner.

“A process known as natural language geo-coding is used on the text to try and derive location coordinates for these locations,” Weidemann said. “This can be taken one step further when you have a user who provides some geo-ebabled Tweets for location reference. For instance, if a user enables GPS sharing on one Tweet, but not the others, I can then use their known locations to narrow down the geo-coding search results for the Tweets without locations.”

The fourth way is far less risky, Weidemann concedes. It uses information gleaned from a public Twitter profile to determine what country and time zone a Tweeter is in.

As part of a research project, Weidemann and fellow researchers developed an application called Twitter2GIS, to analyze the metadata collected by Twitter, including details about the user's hometown, time zone and language. It was then processed by a software program, which mapped and analyzed the data, searching for trends.

Results

PhotoHere's what they found: during a one-week sampling period, some 20% of the Tweets they collected showed the user's location to an accuracy of street level or better. Many also revealed their physical location directly through active location monitoring or GPS coordinates.

An additional 2.2% of all Tweets – about 4.4 million a day – provided so-called "ambient" location data, where the user might not be aware that they are divulging their location.

"The downside is that mining this kind of information can also provide opportunities for criminal misuse of data," Weidemann said. "My intent is to educate social media users and inform the public about their privacy."

As a grad school project Weidemann has developed a site called geosocialfootprint.com to keep social media users informed on privacy issues.

Decreasing geo-social footprint

“Not only does the site help them visualize that risk in a map, but it also points out areas of concern, provides a basic risk assessment, and also tries to provide some dynamic suggestions on decreasing a geo-social footprint,” he said.

For Twitter users worried that they might be revealing too much information, the social media site provides some documentation on how to disable geo Tweets and instructions for deleting your old Tweets. 

In the meantime, Weidemann hopes social media users, include those active on Twitter, begin to think more about privacy and exercise more caution. There's a lot more information out there than you think.

“I think most people would be shocked at the results if they paid an investigator to collect information on themselves,” Weidemann said. “I have received feedback already from shocked users, and for now I'm doing nothing more than helping them visualize their Tweets.”

It's especially worrisome, he says, for teenagers and children who use social media. Not only do they open themselves up to location privacy matters but also general privacy concerns.


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